Late Quaternary paleoenvironmental changes in the southeastern Yellow Sea, Korea

A 34-meter-long AMS 14C-dated sediment core was examined in order to reconstruct the paleoenvironmental changes that have taken place in the southeastern Yellow Sea during the last 16,600 years. To achieve this, we analyzed the geochemical compositions of organic matter, the benthic foraminiferal assemblages, and the stable isotopes of benthic foraminiferal tests. The organic geochemical results show that terrigenous organic matter was dominant in the southeastern Yellow Sea between 16,600 and 4300 cal. yr BP, probably due to the influence of river runoff; marine organic matters, originating from surface primary productivity, began increasing drastically after 4300 cal. yr BP. Benthic foraminiferal assemblages reveal that brackish species were dominant before 3500 cal. yr BP, but the saline species dominated after this time. The δ18O values of the benthic foraminifer Cibicides lobatulus showed that a change from high-amplitude to low-amplitude fluctuations took place at 3500 cal. yr BP. These multi-results indicate that the southeastern Yellow Sea changed from an estuarine to a modern marine shelf environment, probably due to the inflow of the Yellow Sea Warm Current, between 4300 and 3500 cal. yr BP. The time discrepancy of 800 years indicates that a modern marine shelf environment was not fully developed in the southeastern Yellow Sea until 3500 cal. yr BP, even though the sea began to be influenced by the oceanic current at 4300 cal. yr BP